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Benjamin Franklin, Jared Sparks (1856). “The Works of Benjamin Franklin: Containing Several Political and Historical Tracts Not Included in Any Former Edition, and Many Letters, Official and Private Not Hitherto Published; with Notes and a Life of the Author”, p.226
Albert Einstein (2015). “Bite-Size Einstein: Quotations on Just About Everything from the Greatest Mind of the Twentieth Century”, p.40, St. Martin's Press